Head-mounted display apparatus

ABSTRACT

A head-mounted display apparatus includes a display unit including a plurality of emissive areas which displays images and a plurality of transmissive areas disposed between the emissive areas and which transmits light from external light sources, a first optical element which receives and converges light emitted from the display unit onto a predetermined area, and a second optical element disposed opposite to the first optical element with respect to the display unit and which receives and diverges light incident toward the display unit from an outside.

This application claims priority to Korean Patent Application No.10-2014-0118016, filed on Sep. 4, 2014, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

One or more embodiments relate to a head-mounted display apparatus, andmore particularly, to a see-through head-mounted display apparatus thatenables a user to perceive not only an image that is displayed by thesee-through head-mounted display apparatus, but also a background at therear side of the see-through head-mounted display apparatus.

2. Description of the Related Art

In general, a head-mounted display apparatus, which typically has aglasses-like shape or a helmet-like shape and may be mounted on a user'shead, enables the user to perceive an image that is displayed in frontof the user's eyes. Research on a see-through head-mounted displayapparatus that enables a user to perceive not only an image that isdisplayed in front of the user's eyes but also a background at the rearside of the see-through head-mounted display apparatus has been carriedout.

SUMMARY

In a conventional see-through head-mounted display apparatus, abackground image may be distorted by an optical element that is disposedbetween a user's eyes and display apparatus to obtain a shortest focallength.

One or more embodiments include a see-through head-mounted displayapparatus, where a background image displayed therethrough is notdistorted and a display unit thereof is disposed substantially close toan eye of a user when the head-mounted display apparatus is mounted onthe head of the user.

According to exemplary embodiments, a head-mounted display apparatusincludes a display unit including a plurality of emissive areas whichdisplays images and a plurality of transmissive areas disposed betweenthe emissive areas and which transmits external light; a first opticalelement receives and converges light emitted from the display unit ontoa predetermined area; and a second optical element disposed oppositeside to the first optical element with respect to the display unit whichreceives and diverges light incident toward the display unit from theoutside.

In an exemplary embodiment, an absolute value of a focal length of thefirst optical element may be substantially equal to an absolute value ofa focal length of the second optical element.

In an exemplary embodiment, a focal length of the first optical elementmay be about 20 centimeters (

) or more.

In an exemplary embodiment, the first optical element may include apositive lens, and the second optical element may include a negativelens.

In an exemplary embodiment, at least one of the first optical elementand the second optical element may include a Fresnel lens or aholographic optical element (“HOE”) lens.

In an exemplary embodiment, the display unit may include a plurality ofpixels, and each of the plurality of pixels may include a first emissionportion, a second emission portion and a third emission portion, whichare disposed in the emissive areas, and a transmissive window which isdisposed in the transmissive areas and adjacent to the first emissionportion, the second emission portion and the third emission portion.

In an exemplary embodiment, the head-mounted display apparatus mayfurther include a frame which accommodates the display unit, the firstoptical element, and the second optical element and configured to bemounted on a user's head.

According to exemplary embodiments, a head-mounted display apparatusincludes a display unit including a plurality of emissive areas whichdisplays images and a plurality of transmissive areas disposed betweenthe emissive areas and which transmits external light; a first opticalelement which receives light emitted from the display unit, where thefirst optical element converts light emitted from the emissive areasinto polarized light in a first direction, and converts external lightthat has been transmitted through the transmissive areas into polarizedlight in a second direction; and a second optical element which receiveslight transmitted through the first optical element, where the secondoptical element converges the polarized light in the first directiononto a predetermined area and transmits the polarized light in thesecond direction substantially in the same direction as an incidentdirection thereof on the second optical element.

In an exemplary embodiment, the first optical element may include: apolarizer disposed to correspond to the emissive areas and thetransmissive areas; and a liquid crystal layer which receives lighttransmitted through the polarizer and including a first liquid crystaldisposed to correspond to the emissive areas and a second liquid crystaldisposed to correspond to the transmissive areas.

In an exemplary embodiment, the second optical element may include: afirst medium whose refractive index changes depending on a polarizationdirection of incident light; and a second medium in contact with thefirst medium and having a smaller refractive index than a maximumrefractive index of the first medium.

In an exemplary embodiment, the first medium may include a liquidcrystal.

In an exemplary embodiment, the first optical element may include: apolarizer disposed to correspond to the emissive areas and thetransmissive areas; and Λ/2 retarder disposed to correspond to theemissive areas or the transmissive areas.

In one embodiment, the first optical element may include: a firstpolarizer disposed to correspond to the emissive areas and convert lightemitted from the emissive areas into polarized light in the firstdirection; and a second polarizer disposed to correspond to thetransmissive areas and which converts external light transmitted throughthe transmissive areas into polarized light in the second direction.

In an exemplary embodiment, each of the first polarizer and the secondpolarizer may include a wire grid polarizer.

In an exemplary embodiment, the display unit may include a plurality ofpixels, and each of the plurality of pixels may include a first emissionportion, a second emission portion and a third emission portion, whichare disposed in the emissive areas, and a transmissive window disposedin the transmissive areas and adjacent to the first emission portion,the second emission portion, and the third emission portion.

In an exemplary embodiment, the head-mounted display apparatus mayfurther include a frame which accommodates the display unit, the firstoptical element and the second optical element and configured to bemounted on a user's head.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other features will become apparent and more readilyappreciated from the following detailed description of embodimentsthereof, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic side-sectional view illustrating an exemplaryembodiment of a head-mounted display apparatus according to theinvention;

FIG. 2 is a schematic side-sectional view illustrating an alternativeexemplary embodiment of a head-mounted display apparatus according tothe invention;

FIG. 3 is a conceptual perspective view illustrating a pixel in adisplay unit of the head-mounted display apparatus of FIG. 1;

FIG. 4 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatusaccording to the invention;

FIG. 5 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatusaccording to the invention;

FIG. 6 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatusaccording to the invention; and

FIG. 7 is a schematic perspective view illustrating an exemplaryembodiment of a head-mounted display apparatus according to theinvention.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. Like reference numerals refer tolike elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, exemplary embodiments of the invention will now bedescribed with reference to accompanying drawings.

FIG. 1 is a schematic side-sectional view illustrating an exemplaryembodiment of a head-mounted display apparatus 100 according to theinvention.

According to an exemplary embodiment, the head-mounted display apparatus100 includes a display unit 10 including a plurality of emissive areasEA which displays images and a plurality of transmissive areas TAdisposed between the emissive areas EA and which transmits externallight, a first optical element 120 disposed in a path of light emittedfrom the display unit 10 to converge light onto a predetermined area(e.g., a predetermined point or region), and a second optical element ordevice 130 disposed opposite to the first optical element 120 withrespect to the display unit 10 to diverge light incident toward thedisplay unit 10 from the outside. Herein, an optical element may be anoptical device including a transmissive optical device which alterstraveling direction or the polarization state of light passingtherethrough, e.g., a lens or a retarder.

The display unit 10 may be a transparent display which enables a user toperceive not only an image displayed by the display unit 10, but also abackground image, and the display unit 10 may include a variety ofelements. In one exemplary embodiment, for example, the display unit 10may include an organic light-emitting display device or a liquid crystaldisplay device. In an exemplary embodiment, where the display unit 10includes an organic light-emitting display device, the display unit 10that is flexible may be provided by forming organic light-emittingdevices on a flexible substrate.

The first optical element 120 receives light emitted from the displayunit 10. In an exemplary embodiment, the first optical element 120 isdisposed between the display unit 10 and a user's eyeball 40. Thus, thefirst optical element 120 may converge light L1 emitted from theemissive areas EA of the display unit 10 on a surface of a crystallinelens 41 of the user's eyeball 40, and then the light converged on thesurface of the crystalline lens 41 may pass through the crystalline lens41 to reach a retina 42 of the user's eyeball 40.

The display unit 10 of the head-mounted display apparatus 100 isdisposed in front of the user's eyeball 40. Since a shortest focallength for a person's eyes is generally about 20 centimeters (cm), incase that the display unit 10 is not spaced apart by about 20 cm or morefrom the user's eyeball 40, it may be difficult for the user to easilyand clearly perceive an image that is displayed on the emissive areas EAincluded in the display unit 10.

In an exemplary embodiment, the first optical element 120 is an opticalelement that converges incident light. Therefore, in such an embodiment,even when a distance between the display unit 10 and the user's eyeball40 is less than 20 cm, the user may clearly and easily perceive an imagedisplayed on the emissive areas EA since light emitted from the emissiveareas EA is converged on the crystalline lens 41 of the user's eyeball40 by the first optical element 120.

According to an exemplary embodiment, since a shortest focal length fora person's eyes is generally about 20 cm, a focal length of the firstoptical element 120 may be about 20 cm or more. The first opticalelement 120 may include a positive lens, but is not limited thereto. Inan exemplary embodiment, the first optical element 120 may include acombination of a variety of lenses that converges parallel light, andthe first optical element 120 may vary in lens shape.

In an exemplary embodiment, as described above, the display unit 10 maybe a transparent display and may include the transmissive areas TA whichtransmit external light. In such an embodiment, where the display unit10 includes the transmissive areas TA, light L2 from a background at therear side of the head-mounted display apparatus 100 may pass through thehead-mounted display apparatus 100 to the user's eyeball 40.

When the light L2 from a background passes through the first opticalelement 120, a background image may be distorted by the first opticalelement 120. In an exemplary embodiment, the head-mounted displayapparatus 100 may include the second optical element 130, and such adistortion of the background image may be effectively prevented by thesecond optical element 130.

The second optical element 130 may be disposed opposite to the firstoptical element 120 with respect to the display unit 10 to diverge thelight L2 incident toward the display unit 10 from a background.

The light L2 incident toward the display unit 10 from a background maypass through the second optical element 130 before the display unit 10.When the light L2 from a background is parallel light, the parallellight may be diverged as passing through the second optical element 130,and the light that is diverged may pass through transmissive areas TA ofthe display unit 10, and thus the light that is diverged may be incidenton the first optical element 120.

The light that is diverged and incident on the first optical element 120may reach the user's eyeball 40 as parallel light by passing through thefirst optical element 120. As the light L2 from a backgroundsequentially travels through the second optical element 130 and thefirst optical element 120, a direction of light that is incident on theuser's eyeball 40 may be substantially the same as the direction of thelight from the background to the head-mounted display apparatus 100,e.g., before passing through the second optical element 130. In anexemplary embodiment, an absolute value of a focal length of the firstoptical element 120 may be substantially equal to an absolute value of afocal length of the second optical element 130 to allow the direction oflight that is incident on the user's eyeball 40 to be substantially thesame as the direction of the light from the background to thehead-mounted display apparatus 100.

Accordingly, in such an embodiment, the user may easily and clearlyrecognize not only an image displayed on the emissive areas EA, but alsoa background image.

In an exemplary embodiment, the second optical element 130 may becomposed of a negative lens, but is not limited thereto. In analternative exemplary embodiment, the second optical element 130 may bea combination of a variety of lenses that diverges parallel incidentlight, and the second optical element 130 may vary in lens shape.

FIG. 2 is a schematic side-sectional view illustrating an alternativeexemplary embodiment of a head-mounted display apparatus 200 accordingto the invention.

Referring to FIG. 2, an exemplary embodiment of the head-mounted displayapparatus 200 includes the display unit 10 including a plurality ofemissive areas EA which displays images and a plurality of transmissiveareas TA disposed between the emissive areas EA and which transmitsexternal light, a first optical element 220 which receives light emittedfrom the display unit 10 to converge light onto a predetermined area,and a second optical element 230 disposed opposite to the first opticalelement 220 with respect to the display unit 10 to diverge lightincident toward the display unit 10 from the outside.

In an exemplary embodiment, the first optical element 220 receives lightemitted from the display unit 10. In such an embodiment, the firstoptical element 220 is disposed between the display unit 10 and theuser's eyeball 40. Thus, the first optical element 220 may convergelight L1 emitted from the emissive areas EA of the display unit 10 onthe crystalline lens 41 of the user's eyeball 40, and thus lightconverged on the crystalline lens 41 may pass through the crystallinelens 41 to reach a retina 42 of the user's eyeball 40.

In an exemplary embodiment, as shown in FIG. 2, the first opticalelement 220 may be a planar lens such as a Fresnel lens or a holographicoptical element (“HOE”) lens. In such an embodiment, the head-mounteddisplay apparatus 200 including the first optical element 220 may have athin thickness.

In an exemplary embodiment, the first optical element 220 may be spacedapart from the display unit 10 as shown in FIG. 2, but not being limitedthereto. In an alternative exemplary embodiment, the first opticalelement 220 may be attached to the display unit 10.

The second optical element 230 may be disposed opposite to the firstoptical element 220 with respect to the display unit 10 to diverge thelight L2 incident toward the display unit 10 from a background.

The second optical element 230 may be a planar lens such as a Fresnellens or a HOE lens substantially similar to the first optical element220. In such an embodiment, the head-mounted display apparatus 200including the second optical element 230 may have a thin thickness.

A Fresnel lens is a lens obtained by dividing a conventional lens intoconcentric annular sections. The Fresnel lens may have a reducedthickness compared to the conventional lens. An HOE lens includes adiffraction pattern, and thus the HOE lens may diffract incident lightto converge or diverge as conventional lenses do.

In an exemplary embodiment, the first optical element 220 and the secondoptical element 230 of the head-mounted display apparatus 200 mayinclude a planar lens such as a Fresnel lens or an HOE lens to reduce athickness and weight of the head-mounted display apparatus 200. However,the invention is not limited thereto. In one alternative exemplaryembodiment, for example, only one of the first optical element 220 andthe second optical element 230 may include a planar lens. In anotheralternative exemplary embodiment, the first optical element 220 and thesecond optical element 230 may include any other type of diffractionoptical element that converges or diverges light.

FIG. 3 is a conceptual perspective view illustrating a pixel in adisplay unit of the head-mounted display apparatus 100 of FIG. 1.

Referring to FIG. 3, the display unit 10 (see FIG. 1) may include aplurality of pixels P. Each of the pixels P includes a first emissionportion SP1, a second emission portion SP2 and a third emission portionSP3, which are disposed in the emissive areas EA, and a transmissivewindow TW that is disposed in the transmissive areas TA and adjacent tothe first emission portion SP1, the second emission portion SP2 and thethird emission portion SP3.

In an exemplary embodiment, the first emission portion SP1, the secondemission portion SP2 and the third emission portion SP3 may each emitlight of predetermined color. In an exemplary embodiment, the firstemission portion SP1, the second emission portion SP2 and the thirdemission portion SP3 may emit light of different colors from each other,and a combination of the light of the different colors emitted from thefirst emission portion SP1, the second emission portion SP2 and thethird emission portion SP3 may realize white light. In one exemplaryembodiment, for example, the first emission portion SP1, the secondemission portion SP2 and the third emission portion SP3 may respectivelyemit light of three primary colors, e.g., red light, green light andblue light, but not being limited thereto.

The light L1 emitted from the first emission portion SP1, the secondemission portion SP2 or the third emission portion SP3 may be refractedwhen passing through the first optical element 120 of FIG. 1 to beconverged on the user's eyeball 40 of FIG. 1.

The transmissive window TW may be defined by an area where only atransparent insulating layer and/or a transparent electrode aredisposed, and thus the transmissive window TW transmits light incidenton the display unit 10 from a background. The transmissive window TW mayhave a higher transmittance than other areas of the display unit 10 (seeFIG. 1). The transmissive window TW may be divided into a plurality ofparts by connection lines CL, which applies power or an electricalsignal to the first emission portion SP1, the second emission portionSP2 and the third emission portion SP3. The connection lines CL mayinclude a scan line, a data line or a power line, for example.

The light L2 incident toward the display unit 10 from a background maypass sequentially through the second optical element 130 (FIG. 1), thetransmissive areas TA of the display unit 10 (see FIG. 1) and the firstoptical element 120 (see FIG. 1) toward the user's eyeball 40 (see FIG.1).

FIG. 4 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatus 300according to the invention.

Referring to FIG. 4, an exemplary embodiment of the head-mounted displayapparatus 300 includes the display unit 10 including a plurality ofemissive areas EA which displays images and a plurality of transmissiveareas TA disposed between the emissive areas EA and which transmitsexternal light, a first optical element 350 which receives light emittedfrom the display unit 10, converts light L1 emitted from the emissiveareas EA into polarized light in a first direction and converts externallight L2 transmitted through the transmissive areas TA into polarizedlight in a second direction perpendicular to the first direction, and asecond optical element 60 which receives light transmitted through thefirst optical element 350 and converges the polarized light in the firstdirection onto a predetermined area and transmits the polarized light inthe second direction without changing a traveling direction thereof,e.g., substantially in the same direction as an incident directionthereof on the second optical element 60.

The display unit 10 may be a transparent display which enables a user toperceive not only an image displayed on the display unit 10, but also abackground image, and the display unit 10 may include a variety ofelements. In one exemplary embodiment, for example, the display unit 10may include an organic light-emitting display device or a liquid crystaldisplay device.

The light L1 emitted from the emissive areas EA and the external lightL2 that is transmitted through the transmissive areas TA may each passthe first optical element 350 and may be polarized in directionsperpendicular to each other.

In an exemplary embodiment, the first optical element 350 may include apolarizer 351 disposed on both the emissive areas EA and thetransmissive areas TA, a liquid crystal layer 352 which receives lightpassed the polarizer 351 and including a first liquid crystal 352 adisposed to correspond to (e.g., to cover or to overlap) the emissiveareas EA and a second liquid crystal 352 b disposed to correspond to thetransmissive areas TA.

Light incident on the polarizer 351 from the emissive areas EA and thetransmissive areas TA may be polarized in a predetermined direction. Thelight L1 emitted from the emissive areas EA is transmitted through thepolarizer 351 and is incident on the first liquid 352 a, and may beconverted into polarized light in the first direction by the firstliquid 352 a. The external light L2 that has been transmitted throughthe transmissive areas TA is transmitted through the polarizer 351 andis incident on the second liquid 352 b, and may be converted intopolarized light in the second direction by the second liquid 352 b.

In an alternative exemplary embodiment, light transmitted through thepolarizer 351 may be polarized light in the second direction. The secondliquid crystal 352 b may be arranged substantially in the same as thesecond direction or in a direction perpendicular to the seconddirection. The polarized light in the second direction that istransmitted through the polarizer 351 may be transmitted through thesecond liquid 352 b without changing a polarization direction due to thesecond liquid crystal 352 b. The first liquid crystal 352 a may bearranged in any direction or in a spiral form instead of in the seconddirection or in a direction perpendicular to the second direction. Apolarization direction of the polarized light in the second directionthat has been transmitted through the polarizer 351 may be changed bythe first liquid crystal 352 a. By adjusting a thickness and anarrangement direction of the first liquid crystal 352 a, light that hasbeen transmitted through the first liquid crystal 352 a may be polarizedin the first direction perpendicular to the second direction. However,the invention is not limited thereto. In one exemplary embodiment, forexample, light that has been transmitted through the polarizer 351 maybe polarized in the first direction instead of the second direction. Apolarization direction of the polarized light that has been transmittedthrough the polarizer 351 may not be changed by the first liquid crystal352 a, but may be changed 90 degrees by the second liquid 352 b.

According to an exemplary embodiment, the second optical element 60 mayinclude a first medium 61 whose refractive index changes depending onthe polarization direction of incident light and a second medium 62which is in contact with the first medium 61 and has a smallerrefractive index than a maximum refractive index of the first medium 61.

A boundary surface between the first medium 61 and the second medium 62may include a convex shape in a direction toward the user's eyeball 40.In one exemplary embodiment, for example, the boundary surface may havesubstantially the same shape as a surface of a Fresnel lens, but notbeing limited thereto.

The first medium 61 may include a liquid crystal 61 a. The refractiveindex of the liquid crystal 61 a of the first medium 61 may be differentdepending on an arrangement direction of the liquid crystal 61 a of thefirst medium 61 and the polarization direction of incident light. In oneexemplary embodiment, for example, the liquid crystal 61 a of the firstmedium 61 may have a refractive index of about 1.7 with respect topolarized light in the first direction and a refractive index of about1.5 with respect to polarized light in the second direction. The secondmedium 62 may be composed of glass or plastic and have a refractiveindex of about 1.5.

In such an embodiment, light polarized in a first direction may berefracted at the boundary surface between the first medium 61 and thesecond medium 62. That is, light emitted from the emissive areas EA maybe refracted at the boundary surface between the first medium 61 and thesecond medium 62, and be converged on the crystalline lens 41 of theuser's eyeball 40.

In such an embodiment, light polarized in the second direction may notbe refracted at the boundary surface between the first medium 61 and thesecond medium 62, and be transmitted through the second optical element60 in substantially the same as a direction of incident light, and fallon the user's eyeball 40.

In such an embodiment, the head-mounted display apparatus 300 may allowthe user to easily and clearly recognize not only an image displayed onthe emissive areas EA, but also a background image without distortion.

FIG. 5 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatus 400according to the invention.

Referring to FIG. 5, an exemplary embodiment of the head-mounted displayapparatus 400 includes the display unit 10 including a plurality ofemissive areas EA which displays images and a plurality of transmissiveareas TA disposed between the emissive areas EA and which transmitsexternal light, a first optical element 450 which receives light emittedfrom the display unit 10, converts light L1 emitted from the emissiveareas EA into polarized light in a first direction and converts externallight L2 transmitted through the transmissive areas TA into polarizedlight in a second direction perpendicular to the first direction, and asecond optical element 60 which receives light that has been transmittedthrough the first optical element 450, converges the polarized light inthe first direction onto a predetermined area and transmits thepolarized light in the second direction substantially in the samedirection as an incident direction thereof on the second optical element60.

The first optical element 450 may include a first polarizer 450 adisposed to correspond to the emissive areas EA and which converts thelight L1 emitted from the emissive areas EA into polarized light in thefirst direction, and a second polarizer 450 b disposed to correspond tothe transmissive areas TA and which converts the external light L2transmitted through the transmissive areas TA into polarized light inthe second direction.

The first polarizer 450 a and the second polarizer 450 b may each be awire grid polarizer and may be alternately arranged with each other onthe display unit 10. The wire grid polarizer may be an array of finemetal wires arranged substantially parallel to each other, which may beefficiently provided by a patterning process.

The display unit 10 and the second optical element 60 shown in FIG. 5may have substantially the same configuration as the configuration inthe head-mounted display apparatus 300 of FIG. 4, and any repetitivedetailed description thereof will be omitted.

FIG. 6 is a schematic side-sectional view illustrating anotheralternative exemplary embodiment of a head-mounted display apparatus 500according to the invention.

Referring to FIG. 6, an exemplary embodiment of the head-mounted displayapparatus 500 includes the display unit 10 including a plurality ofemissive areas EA which displays images and a plurality of transmissiveareas TA disposed between the emissive areas EA, and which transmitsexternal light, the first optical element 550 which receives lightemitted from the display unit 10, converts light L1 emitted from theemissive areas EA into polarized light in a first direction and convertsexternal light L2 that has been transmitted through the transmissiveareas TA into polarized light in a second direction perpendicular to thefirst direction, and the second optical element 60 which receives lightthat has been transmitted through the first optical element 550,converges the polarized light in the first direction onto apredetermined area and transmits the polarized light in the seconddirection substantially in the same direction as an incident directionthereof on the second optical element 60.

The first optical element 550 may include a polarizer 551 disposed tocorrespond to both the emissive areas EA and the transmissive areas TAand a Λ/2 retarder 552 disposed to correspond to either emissive areasEA or transmissive areas TA.

According to an exemplary embodiment, the Λ/2 retarder 552 may bedisposed on areas corresponding to the emissive areas EA. Incident lightfalling on the polarizer 551 from the emissive areas EA and thetransmissive areas TA may be converted into polarized light in thesecond direction by the polarizer 551. The light L1 emitted from theemissive areas EA is transmitted through the polarizer 551 and falls onthe Λ/2 retarder 552, and may be converted into polarized light in thefirst direction perpendicular to the second direction.

However, the invention is not limited thereto. In one alternativeexemplary embodiment, for example, the Λ/2 retarder 552 may be disposedon areas corresponding to the transmissive areas TA. Incident lightfalling on the polarizer 551 from the emissive areas EA and thetransmissive areas TA may be converted into light polarized in the firstdirection by the polarizer 551. The external light L2 that has beentransmitted through the transmissive areas TA is transmitted through thepolarizer 551 and falls on the Λ/2 retarder 552, and may be convertedinto polarized light in the second direction perpendicular to the firstdirection.

The display unit 10 and the second optical element 60 shown in FIG. 6may have substantially the same configuration as that in thehead-mounted display apparatus of FIG. 4, and any repetitive detaileddescription thereof will be omitted.

FIG. 7 is a schematic perspective view illustrating an exemplaryembodiment of a head-mounted display apparatus 1 according to theinvention.

Referring to FIG. 7, an exemplary embodiment of the head-mounted displayapparatus 1 may include a frame 70 including the display unit 10, thefirst optical element 120 or 220, and the second optical element 130 or230 or accommodating the display unit 10, the first optical element 350,450 or 550, and the second optical element 60, and configured to bemounted on a user's head.

Exemplary embodiments of the head-mounted display apparatus 1, 100, 200,300, 400, and 500 may enable a user to easily and clearly recognize notonly an image displayed by the display unit 10, but also a backgroundimage that is transmitted through the display unit 10.

As described above, according to exemplary embodiments set forth herein,a see-through head-mounted display apparatus may be provided withoutdistorting a background image. However, the scope of the inventiveconcept is not limited to this effect.

While one or more embodiments of the invention have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. A head-mounted display apparatus comprising: adisplay unit comprising: a plurality of emissive areas which displaysimages; and a plurality of transmissive areas disposed between theemissive areas and which transmits external light; a first opticalelement attached to the display unit, wherein the first optical elementreceives and converges light emitted from the display unit onto apredetermined area; and a second optical element disposed opposite tothe first optical element with respect to the display unit, wherein thesecond optical element receives and diverges light incident toward thedisplay unit from an outside.
 2. The head-mounted display apparatus ofclaim 1, wherein an absolute value of the focal length of the firstoptical element is substantially equal to an absolute value of a focallength of the second optical element.
 3. The head-mounted displayapparatus of claim 1, wherein the first optical element comprises apositive lens, and the second optical element comprises a negative lens.4. The head-mounted display apparatus of claim 1, wherein at least oneof the first optical element and the second optical element comprises aFresnel lens or a holographic optical element lens.
 5. The head-mounteddisplay apparatus of claim 1, wherein the display unit comprises aplurality of pixels, and each of the plurality of pixels comprises: afirst emission portion, a second emission portion and a third emissionportion, which are disposed in the emissive areas; and a transmissivewindow disposed in the transmissive areas and adjacent to the firstemission portion, the second emission portion and the third emissionportion.
 6. The head-mounted display apparatus of claim 1, furthercomprising: a frame which accommodates the display unit, the firstoptical element and the second optical element, and configured to bemounted on a user's head.
 7. A head-mounted display apparatuscomprising: a display unit comprising: a plurality of emissive areaswhich displays images; and a plurality of transmissive areas disposedbetween the emissive areas and which transmits external light; a firstoptical element attached to the display unit, wherein the first opticalelement receives and converges light emitted from the display unit ontoa predetermined area; and a second optical element disposed opposite tothe first optical element with respect to the display unit, wherein thesecond optical element receives and diverges light incident toward thedisplay unit from an outside, wherein the first optical element receivesand converges light emitted from the plurality of emissive areasseparated by the plurality of transmissive areas, an absolute value of afocal length of the first optical element is substantially equal to anabsolute value of a focal length of the second optical element, and thefocal lengths of the first optical element and the second opticalelement are fixed.
 8. The head-mounted display apparatus of claim 1,wherein a focal length of the first optical element is about 20centimeters or more.